DIY 11 HP flathead minibike
- Thread starter nico_v
- Start date
Thanks! I have been really lucky with my machines, would you believe me if I said I paid $150 for that lathe? And there was absolutely nothing wrong with it! And I have another larger lathe that I also got for $150, and a horizontal mill for $100 
Counting myself very lucky there, but I've had plenty of bad luck in other areas so I guess in the end it all evens out.
Probably would've had the cheapest machine park in Europe if it weren't for the vertical mill which I paid around $1700 for (used). But I use them all the time, I've more than made my money back in parts that I didn't have to buy because I could make them myself.
Machining a billet rod is something I have considered, if I can find the right material and rod bearings. I could probably make the bearings myself too but then I'd need to figure out what material to use for them.
Counting myself very lucky there, but I've had plenty of bad luck in other areas so I guess in the end it all evens out.Probably would've had the cheapest machine park in Europe if it weren't for the vertical mill which I paid around $1700 for (used). But I use them all the time, I've more than made my money back in parts that I didn't have to buy because I could make them myself.
Machining a billet rod is something I have considered, if I can find the right material and rod bearings. I could probably make the bearings myself too but then I'd need to figure out what material to use for them.
So as you saw in my previous update, the TM28 is in place. I've also balanced the flywheel, here's a new video:
https://youtu.be/-c-eHBiV8Ko
Mikuni TM28 carb, intake, flywheel balance - Minibike tuning part 3 - YouTube
I'm currently working on stretching the frame
I'm thinking of maybe skipping the long jackshaft that has a "counter bearing" (?) attached to the frame, and just use the short jackshaft that comes with the torque converter. It'd make my life a lot easier. The question is if it's going to hold up? I think it will but I'd like to hear some opinions. The gear will be less than an inch from the rear of the backplate and bearing.
https://youtu.be/-c-eHBiV8Ko
Mikuni TM28 carb, intake, flywheel balance - Minibike tuning part 3 - YouTube
I'm currently working on stretching the frame
I'm thinking of maybe skipping the long jackshaft that has a "counter bearing" (?) attached to the frame, and just use the short jackshaft that comes with the torque converter. It'd make my life a lot easier. The question is if it's going to hold up? I think it will but I'd like to hear some opinions. The gear will be less than an inch from the rear of the backplate and bearing.
First off, great third video. I commented on the YouTube page. I haven't used the "Torque-A-Verter" or TAV systems, but many here have. They seem to be used by the guys who use the OHV engines, so they may not even be looking in this thread. I always ask [MENTION=31879]CarPlayLB[/MENTION] if I have questions, but he ignores me about half the time.
From what I have seen, those systems will hold up with a lot of horsepower. I am sure you could install an inner and outer bearing carrier if you were worried about the torque, like drag bikes, sleds, and Jr. dragsters.
From what I have seen, those systems will hold up with a lot of horsepower. I am sure you could install an inner and outer bearing carrier if you were worried about the torque, like drag bikes, sleds, and Jr. dragsters.
Thanks!
My main worry is the shaft itself, it's only 5/8'' I think. But I think it's worth a shot. Worst case is the shaft bends or the backplate bends or cracks, either way it should be easily fixable if something does happen.
There's 2 bearings in the backplate, one in the front and one in the back but I'd like to avoid putting bearings (and carriers) in the frame because skipping those allows me to reposition the engine and/or change the angle of the plate if needed.
This is what the back of it looks like, my sprocket needs to be about 3/4 inch from the rear bearing in order to align with the sprocket on the rear wheel.
I think I'll try with just the short shaft just to see what happens, maybe shaft straightening or backplate repair would make a nice video too
My main worry is the shaft itself, it's only 5/8'' I think. But I think it's worth a shot. Worst case is the shaft bends or the backplate bends or cracks, either way it should be easily fixable if something does happen.
There's 2 bearings in the backplate, one in the front and one in the back but I'd like to avoid putting bearings (and carriers) in the frame because skipping those allows me to reposition the engine and/or change the angle of the plate if needed.
This is what the back of it looks like, my sprocket needs to be about 3/4 inch from the rear bearing in order to align with the sprocket on the rear wheel.
I think I'll try with just the short shaft just to see what happens, maybe shaft straightening or backplate repair would make a nice video too
Thanks!
My main worry is the shaft itself, it's only 5/8'' I think. But I think it's worth a shot. Worst case is the shaft bends or the backplate bends or cracks, either way it should be easily fixable if something does happen.
There's 2 bearings in the backplate, one in the front and one in the back but I'd like to avoid putting bearings (and carriers) in the frame because skipping those allows me to reposition the engine and/or change the angle of the plate if needed.
This is what the back of it looks like, my sprocket needs to be about 3/4 inch from the rear bearing in order to align with the sprocket on the rear wheel.
View attachment 105332
I think I'll try with just the short shaft just to see what happens, maybe shaft straightening or backplate repair would make a nice video too
My main worry is the shaft itself, it's only 5/8'' I think. But I think it's worth a shot. Worst case is the shaft bends or the backplate bends or cracks, either way it should be easily fixable if something does happen.
There's 2 bearings in the backplate, one in the front and one in the back but I'd like to avoid putting bearings (and carriers) in the frame because skipping those allows me to reposition the engine and/or change the angle of the plate if needed.
This is what the back of it looks like, my sprocket needs to be about 3/4 inch from the rear bearing in order to align with the sprocket on the rear wheel.
View attachment 105332
I think I'll try with just the short shaft just to see what happens, maybe shaft straightening or backplate repair would make a nice video too
Honestly, as I was watching the latest video, I expected that to happen. That chain was WAY too tight and on top of that you have a swingarm. As the rear suspension compresses when you hit the gas, the chain tensions even more thus breaking the backplate. I think you'd be fine just ordering another backplate (Comet is always better) and not relocating the bearing. But loosen up the chain and/or add a spring tensioner on the bottom.
The backplate should be able to stand without the counter bearing IF the chain stays at a reasonable tension but then again, I'm saying that as a keyboard warrior.
The backplate should be able to stand without the counter bearing IF the chain stays at a reasonable tension but then again, I'm saying that as a keyboard warrior.
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